Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/10—Esters; Ether-esters
  • C08K5/101—Esters; Ether-esters of monocarboxylic acids
  • C08K5/103—Esters; Ether-esters of monocarboxylic acids with polyalcohols
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
  • G11B7/253—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates
  • G11B7/2533—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising resins
  • G11B7/2534—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising resins polycarbonates [PC]

Definitions

• the present invention relates to a polycarbonate resin composition for use in the production of a substrate for an optical information medium. More particularly, the present invention is concerned with a polycarbonate resin composition for use in the production of a substrate for an optical information medium, comprising (A) an aromatic polycarbonate resin having a weight average molecular weight of from 13,000 to 18,000, wherein the aromatic polycarbonate resin (A) is produced by subjecting an aromatic dihydroxy compound and a carbonic diester to a transesterification reaction, and is substantially free of a chlorine atom, and (B) a partial ester obtained from a saturated aliphatic carboxylic acid having 10 to 30 carbon atoms and a dito hexahydric alcohol, the partial ester (B) having an acid value of from 2 to 20 mgKOH.
• the polycarbonate resin composition of the present invention in the production of a substrate for an optical information medium is advantageous in that a substrate (for an optical information medium) which has high mechanical strength and in which the occurrence of a “cloud” (i.e., haze) is suppressed, can be produced by the so-called “high-cycle molding” (i.e., the molding can be performed with a short cycle time). Therefore, the polycarbonate resin composition of the present invention can be very advantageously used in the production of a substrate for an optical information medium, such as an optical disc (e.g., a CD or a DVD).
• an optical disc e.g., a CD or a DVD
• Polycarbonates have been widely used in various fields as engineering plastics having excellent properties with respect to heat resistance, impact resistance and transparency. Especially, due to the recent rapid progress of information technology, there has been a growing demand for polycarbonates for producing storage media for music and images, and storage media for digital information (such as a storage medium for a personal computer).
• polycarbonates have become indispensable resins for producing optical discs and optical cards, such as a CD, a CD-ROM, a CD-R, a DVD-ROM and a DVD-R.
• a substrate for an optical information medium such as an optical disc
• Polycarbonates for use in the production of such a substrate need to have high transferability and excellent optical properties, such as low birefringence. Therefore, low molecular weight polycarbonates having a weight average molecular weight of about 15,500 and having a high melt fluidity have hitherto been used in the production of the substrates for the optical information media.
• the transesterification polycarbonates have the following problems.
• a substrate for an optical information medium hereinafter frequently referred to as a “disc”
• the substrate produced exhibits poor properties, as compared to the properties of a substrate produced from a phosgene process polycarbonate.
• problems occur not only in that the disc produced exhibits low mechanical strength, but also in that marked occurrence of a cloud (i.e., haze) is encountered during the molding, thus rendering it impossible to obtain an excellent substrate for an optical information medium.
• the transesterification polycarbonates have a defect in that, when an attempt is made to shorten the time of molding cycle in order to improve the productivity of the disc (i.e., when a disc is produced by the “high-cycle molding”), the occurrence of a cloud is likely to be more vigorous. Therefore, it has been desired to improve the transesterification polycarbonates with respect to these properties.
• Unexamined Japanese Patent Application Laid-Open Specification No. Sho 60-113201 proposes a molded article for optical use, comprising a polycarbonate composition containing 0.01 to 0.2 part by weight, relative to 100 parts by weight of the polycarbonate, of a monoglyceride of a saturated aliphatic monoacid having 16 to 22 carbon atoms. It is considered that the monoglyceride used in this patent document is a commercially available product. In this connection, it should be noted that, as described below, the acid value of a commercially available monoglyceride of an aliphatic acid is approximately 1 mgKOH. Therefore, the acid value of the monoglyceride used in this patent document does not fall in the acid value range (of from 2 to 20 mgKOH) prescribed for the partial ester used in the present invention.
• Unexamined Japanese Patent Application Laid-Open Specification No. Hei 7-169092 proposes a substrate for an optical information medium, comprising a polycarbonate composition containing a mold release agent which is comprised of a C 10 -C 30 aliphatic acid ester (e.g., glycerol monostearate) and which has a pH value of 7 or less, wherein the mold release agent is present in an amount of 0.5% by weight or less, based on the weight of the polycarbonate composition.
• a mold release agent which is comprised of a C 10 -C 30 aliphatic acid ester (e.g., glycerol monostearate) and which has a pH value of 7 or less, wherein the mold release agent is present in an amount of 0.5% by weight or less, based on the weight of the polycarbonate composition.
• the aliphatic acid ester used therein has a pH value of from 4.0 to 6.5.
• the acid value of the partial ester used in the present invention (which is in the range of from 2 to 20 mgKOH) is expressed in terms of a pH value which is obtained by taking into consideration the operation conditions as described in this patent document, the pH value in the range of from about 1.75 to about 2.75 is obtained. Therefore, the acid value of the partial ester used in this patent document does not fall in the acid value range (of from 2 to 20 mgKOH) prescribed for the partial ester used in the present invention.
• Unexamined Japanese Patent Application Laid-Open Specification No. Hei 8-73724 proposes a composition comprising 100 parts by weight of an aromatic polycarbonate resin having a terminal hydroxyl content of from 2 to 40 mole % and a molecular weight distribution (Mw/Mn) of from 2.0 to 2.8 as measured by gel permeation chromatography, and 0.01 to 0.1 part by weight of a partial ester obtained from an aliphatic carboxylic acid and a polyhydric alcohol. It is considered that the partial ester used in this patent document is a commercially available product.
• the acid value of a commercially available partial ester is approximately 1 mgKOH. Therefore, the acid value of the partial ester used in this patent document does not fall in the acid value range (of from 2 to 20 mgKOH) prescribed for the partial ester used in the present invention.
• a polycarbonate resin composition comprising a polycarbonate resin produced by the transesterification process and a partial ester obtained from a saturated aliphatic carboxylic acid having 10 to 30 carbon atoms and a di- to hexahydric alcohol, wherein the partial ester has an acid value of from 2 to 20 mgKOH.
• this polycarbonate resin composition is advantageous not only in that the substrate produced exhibits a greatly improved mechanical strength and remarkable suppression of occurrence of a cloud (i.e., haze), but also in that the polycarbonate resin composition exhibits excellent suitability for high-cycle molding (i.e., excellent aptitude for being molded with a short cycle time).
• a cloud i.e., haze
• the polycarbonate resin composition exhibits excellent suitability for high-cycle molding (i.e., excellent aptitude for being molded with a short cycle time).
• a primary object of the present invention to provide a polycarbonate resin composition which is advantageous not only in that it can be used in the production of an excellent substrate for an optical information medium, such as an optical disc (e.g., a CD or a DVD), the substrate exhibiting high mechanical strength and remarkable suppression of occurrence of a cloud (i.e., haze), but also in that the resin composition exhibits excellent suitability for high-cycle molding (i.e., excellent aptitude for being molded with a short cycle time).
• an optical information medium such as an optical disc (e.g., a CD or a DVD)
• the substrate exhibiting high mechanical strength and remarkable suppression of occurrence of a cloud (i.e., haze)
• the resin composition exhibits excellent suitability for high-cycle molding (i.e., excellent aptitude for being molded with a short cycle time).
• a polycarbonate resin composition for use in the production of a substrate for an optical information medium comprising:
• aromatic polycarbonate resin (A) is produced by subjecting an aromatic dihydroxy compound and a carbonic diester to a transesterification reaction, and is substantially free of a chlorine atom, and
• aromatic polycarbonate resin (A) is produced by subjecting an aromatic dihydroxy compound and a carbonic diester to a transesterification reaction, and is substantially free of a chlorine atom, and
• the amount of the heterounit (2) being from 0.03 to 0.20 mole %, based on the total molar amount of the recurring units (1).
• the polycarbonate resin composition of the present invention for use in the production of a substrate for an optical information medium is a composition comprising:
• aromatic polycarbonate resin (A) is produced by subjecting an aromatic dihydroxy compound and a carbonic diester to a transesterification reaction, and is substantially free of a chlorine atom, and
• aromatic dihydroxy compound means a compound represented by the formula: HO—Ar—OH
• aromatic group Ar is a divalent aromatic group represented by the formula: —Ar 1 —Y——Ar 2 —, wherein each of Ar 1 and Ar 2 independently represents a divalent C 5 -C 70 carbocyclic or heterocyclic aromatic group, and Y represents a divalent C 1 -C 30 alkane group.
• At least one hydrogen atom thereof may be replaced by a substituent which does not adversely affect the transesterification reaction for producing a polycarbonate resin, such as a halogen atom, an alkyl group having from 1 to 10 carbon atoms, an alkoxy group having from 1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano group, an ester group, an amide group or a nitro group.
• a substituent which does not adversely affect the transesterification reaction for producing a polycarbonate resin such as a halogen atom, an alkyl group having from 1 to 10 carbon atoms, an alkoxy group having from 1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano group, an ester group, an amide group or a nitro group.
• heterocyclic aromatic groups include an aromatic group having in a skeleton thereof at least one hetero atom, such as a nitrogen atom, an oxygen atom or a sulfur atom.
• Examples of divalent aromatic groups Ar 1 and Ar 2 include an unsubstituted or substituted phenylene group, an unsubstituted or substituted biphenylene group and an unsubstituted or substituted pyridylene group. Substituents for Ar 1 and Ar 2 are as described above.
• divalent alkane groups Y include or ganic groups respectively represented by the following formulae:
• divalent aromatic groups Ar which are represented by the above-mentioned formula:
• divalent aromatic groups Ar include those which are represented by the following formula: —Ar 1 -Z-Ar 2 —
• divalent aromatic groups Ar which are represented by the above-mentioned formula:
• R 7 , R 8 , m and n are as defined above.
• divalent aromatic groups Ar include an unsubstituted or substituted phenylene group, an unsubstituted or substituted naphthylene group, an unsubstituted or substituted biphenylene group and an unsubstituted or substituted pyridylene group.
• aromatic dihydroxy compounds may be used individually or in combination.
• aromatic dihydroxy compounds there can be mentioned bisphenol A.
• the carbonic diester used in the present invention is represented by the following formula:
• each of Ar 3 and Ar 4 which independently represents a monovalent carbocyclic or heterocyclic aromatic group, at least one hydrogen atom may be replaced by a substituent which does not adversely affect the transesterification reaction for producing the polycarbonate resin, such as a halogen atom, an alkyl group having from 1 to 10 carbon atoms, an alkoxy group having from 1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano group, an ester group, an amide group or a nitro group.
• Ar 3 and Ar 4 may be the same or different.
• monovalent aromatic groups Ar 3 and Ar 4 include a phenyl group, a naphthyl group, a biphenyl group and a pyridyl group. These groups may or may not be substituted with the abovementioned substituent or substituents.
• Preferred examples of monovalent aromatic groups Ar 3 and Ar 4 include those which are represented by the following formulae:
• carbonic diesters include di(unsubstituted or substituted)aryl carbonate compounds represented by the following formula:
• diaryl carbonate compounds preferred are those having a symmetrical configuration, for example, di(unsubstituted)phenyl carbonate and di(lower alkylsubstituted)phenyl carbonates, e.g., ditolyl carbonate and di-t-butylphenyl carbonate. Especially preferred is di(unsubstituted)phenyl carbonate, which has the simplest structure. These carbonic diesters may be used individually or in combination.
• the ratio (i.e., a charging ratio) of the aromatic dihydroxy compound to the carbonic diester varies depending on the types of the aromatic dihydroxy compound and carbonic diester employed and other polymerization conditions, e.g., the reaction temperature.
• the carbonic diester is generally used in an amount of from 0.9 to 2.5 moles, preferably from 0.95 to 2.0 moles, more preferably from 0.98 to 1.5 moles, per mole of the aromatic dihydroxy compound.
• an aromatic monohydroxy compound may be used for changing the terminal groups, or adjusting the molecular weight of the polycarbonate resin (A).
• the production of a polycarbonate resin is conducted by a transesterification process which is a process wherein a condensation polymerization of the aromatic dihydroxy compound and the carbonic diester is performed by transesterification in the molten state while heating in the presence or absence of a catalyst under reduced pressure and/or under an inert gas flow.
• a transesterification process which is a process wherein a condensation polymerization of the aromatic dihydroxy compound and the carbonic diester is performed by transesterification in the molten state while heating in the presence or absence of a catalyst under reduced pressure and/or under an inert gas flow.
• the mode of the transesterification process, the polymerization equipment and the like are not specifically limited.
• reactors employable for performing the transesterification reaction include an agitation type reactor vessel, a wiped film type reactor, a centrifugal wiped film evaporation type reactor, a surface renewal type twin-screw kneading reactor, a twin-screw horizontal agitation type reactor, a wall-wetting fall reactor, a free-fall polymerizer having a perforated plate, and a guide-wetting fall polymerizer having a perforated plate and at least one guide (e.g., a wire) provided in association with the perforated plate (e.g., a wire-wetting fall reactor having a perforated plate).
• the transesterification reaction can be easily performed using these various types of reactors individually or in combination.
• the production of the polycarbonate resin (A) can also be performed by the solid-state polymerization process, in which a molten-state transesterification process is first conducted to obtain a prepolymer, and the obtained prepolymer is then subjected to a solid-state polymerization under reduced pressure and/or under an inert gas flow, thereby increasing the polymerization degree of the prepolymer.
• a molten-state transesterification process is first conducted to obtain a prepolymer, and the obtained prepolymer is then subjected to a solid-state polymerization under reduced pressure and/or under an inert gas flow, thereby increasing the polymerization degree of the prepolymer.
• the free-fall polymerizer having a perforated plate reference can be made, for example, to U.S. Pat. No. 5,596,067.
• the guide-wetting fall polymerizer reference can be made, for example, to U.S. Pat. Nos. 5,589,564 and 5,840
• a transesterification reaction can be carried out in the absence of a catalyst. However, if it is desired to accelerate the polymerization, the polymerization can be effected in the presence of a catalyst.
• the polymerization catalysts which are customarily used in the art can be used without particular limitation. Examples of such catalysts include hydroxides of an alkali metal and of an alkaline earth metal, such as lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide;
• alkali metal salts of, alkaline earth metal salts of and quaternary ammonium salts of boron hydride and aluminum hydride such as lithium aluminum hydride, sodium boron hydride and tetramethyl ammonium boron hydride
• hydrides of an alkali metal and of an alkaline earth metal such as lithium hydride, sodium hydride and calcium hydride
• alkoxides of an alkali metal and of an alkaline earth metal such as lithium methoxide, sodium ethoxide and calcium methoxide
• aryloxides of an alkali metal and of an alkaline earth metal such as lithium phenoxide, sodium phenoxide, magnesium phenoxide, LiO—Ar—OLi wherein Ar represents an arylene group, and NaO—Ar—ONa wherein Ar is as defined above; organic acid salts of an alkali metal and of an alkaline earth metal, such as lithium acetate, calcium acetate and sodium benzoate; zinc compounds, such as zinc oxide, zinc acetate and zinc phenoxide; boron compounds, such as boron oxide, boric acid, sodium borate, trimethyl borate, tributyl borate, triphenyl borate, ammonium borates represented by the formula: (R 1 R 2 R 3 R 4 )NB(R 1 R 2 R 3 R 4 ), and phosphonium borates represented by the formula: (R 1 , R 2 , R 3 , R 4 )PB(R 1 R 2 R 3 R 4 ), wherein R 1 , R 2 ,
• silicon compounds such as silicon oxide, sodium silicate, tetraalkylsilicon, tetraarylsilicon and diphenyl-ethyl-ethoxysilicon
• germanium compounds such as germanium oxide, germanium tetrachloride, germanium ethoxide and germanium phenoxide
• tin compounds such as tin oxide, dialkyltin oxide, dialkyltin carboxylate, tin acetate, tin compounds having an alkoxy group or aryloxy group bonded to tin, such as ethyltin tributoxide, and organotin compounds
• lead compounds such as lead oxide, lead acetate, lead carbonate, basic lead carbonate, and alkoxides and aryloxides of lead or organolead
• lead compounds such as lead oxide, lead acetate, lead carbonate, basic lead carbonate, and alkoxides and aryloxides of lead or organolead
• onium compounds such as a quaternary ammonium salt, a quaternary phosphonium salt and a quaternary arsonium salt
• antimony compounds such as antimony oxide and antimony acetate
• manganese compounds such as manganese acetate, manganese carbonate and manganese borate
• titanium compounds such as titanium oxide and titanium alkoxides and titanium aryloxide
• zirconium compounds such as zirconium acetate, zirconium oxide, zirconium alkoxide, zirconium aryloxide and zirconium acetylacetone.
• the catalysts can be used individually or in combination.
• the amount of the catalyst used is generally in the range of from 10 ⁇ 8 to 1 part by weight, preferably from 10 ⁇ 7 to 10 ⁇ 1 part by weight, relative to 100 parts by weight of the aromatic dihydroxy compound.
• the polycarbonate resin (A) used in the present invention has a weight average molecular weight of from 13,000 to 18,000, preferably from 13,500 to 17,000, more preferably from 14,000 to 16,000.
• weight average molecular weight is larger than the abovementioned range, the melt fluidity of the polycarbonate resin becomes unsatisfactory, so that the polycarbonate resin cannot be used for producing a substrate for an optical information medium having a high recording density, such as a DVD.
• the weight average molecular weight is smaller than the above-mentioned range, the mechanical strength of the substrate produced becomes unsatisfactory.
• the weight average molecular weight of the polycarbonate resin can be measured by gel permeation chromatography (GPC) using TOSOH TSK-GEL column Nos. G5000HXL/G4000HXL/G4000HXL (each manufactured and sold by Tosoh Corporation, Japan), tetrahydrofuran (as a solvent) and a polystyrene gel column.
• GPC gel permeation chromatography
• the aromatic polycarbonate resin (A) comprises a plurality of aromatic polycarbonate main chains, each comprising recurring units each independently represented by the following formula (1):
• the amount of the heterounit (2) being from 0.03 to 0.20 mole %, based on the total molar amount of the recurring units (1).
• heterounit (2) is a unit represented by the following formula (2′):
• the amount of the heterounit (2) is less than 0.03 mole %, based on the total molar amount of the recurring units (1), the transferability of the resin composition tends to become unsatisfactory.
• the amount of the heterounit (2) is more than 0.20 mole %, based on the total molar amount of the recurring units (1), occurrence of a cloud tends to be caused and the mechanical strength of the produced substrate tends to become unsatisfactory.
• the amount of the heterounit (2) is more preferably in the range of from 0.04 to 0.18 mole %, still more preferably in the range of from 0.05 to 0.15 mole %, based on the total molar amount of the recurring units (1).
• the determination of each of recurring units (1) and heterounits (2) can be conducted, for example, by a method in which the polycarbonate resin is completely hydrolyzed, and the resultant hydrolysis mixture is analyzed by reversed phase liquid chromatography (the analysis by reversed phase liquid chromatography can be conducted under the conditions as described below in the Examples).
• the hydrolysis of the polycarbonate resin it is preferred that the hydrolysis is conducted at room temperature by the method described in “Polymer Degradation and Stability” 45 (1994), 127-137.
• the hydrolysis by this method is advantageous in that the complete hydrolysis of a polycarbonate resin can be achieved by simple operation without the danger of occurrence of side reactions during the hydrolysis.
• the hydrolysis of the polycarbonate resin is conducted at room temperature (25° C.).
• heterounits (2) are introduced into the polycarbonate main chains by using a specific aromatic dihydroxy compound having a carboxyl group, which, when subjected to a transesterification reaction with a carbonic diester, forms the heterounits (2), to thereby introduce a branched structure.
• the polycarbonate resin used in the present invention can be produced without using the above-mentioned specific compound, specifically, by a second method in which recurring units (1) of the polycarbonate main chains are converted so as to form and contain therein the heterounits during the polymerization process by choosing appropriate polymerization conditions, such as polymerization temperature, type of catalyst, and residence time.
• polymerization conditions such as polymerization temperature, type of catalyst, and residence time.
• the above-mentioned second method it is preferred to use the above-mentioned second method, since this method enables easy production of a polycarbonate resin which is useful for preparing a resin composition which is advantageous not only in that it exhibits substantial freedom from the occurrence of optical defects when the disc produced from the composition is subjected to a test of resistance to moist heat, but also in that the composition exhibits an excellent balance of the mechanical properties of the disc produced from the composition and the moldability of the composition.
• the test can be performed by, for example, the following method.
• Three disc-shaped substrates (e.g., a substrate for a DVD-R (hereinafter, frequently referred to simply as an “optical disc substrate”) are produced by subjecting a polycarbonate resin composition to an injection molding, using an injection molding machine for producing optical discs (J35EL II-DK, manufactured and sold by THE JAPAN STEEL WORKS. LTD., Japan), at a molding temperature of 370° C., and a mold temperature of 120° C.
• the thus obtained optical disc substrates are subjected to, for example, sputtering and formation of a photosensitive layer, thereby obtaining three optical discs.
• the thus obtained three optical discs are allowed to stand at 90° C.
• the optical discs are then observed through a magnifying lens to see whether or not the discs have a craze-like optical defect having a diameter of 200 ⁇ m or more.
• the evaluation of the resistance to moist heat is made in accordance with the following criteria.
• the evaluation of the resistance to moist heat there can also be performed a test for the degree of the occurrence of errors in recording and reading with a laser beam, by using a testing device for evaluating the performance of an optical disc in recording and reading with a laser beam, to thereby evaluate the performance of the discs as optical information media.
• the polycarbonate resin used in the present invention may have a structure in which heterounits other than the heterounits (2) are introduced into the polycarbonate main chains by using a multifunctional compound.
• multifunctional compounds include those described in the U.S. 2002/0183428 A1, which are compounds each having three or more functional groups selected from the group consisting of a phenolic hydroxyl group and a carboxyl group.
• transesterification polycarbonate resins tend to have a high ratio of terminal hydroxyl groups in all terminal groups.
• the polycarbonate resin has terminal hydroxyl groups in an amount of from 5 to 50 mole %, based on the total molar amount of the terminal groups of the polycarbonate resin.
• the amount of the terminal hydroxyl groups is more preferably from 10 to 40 mole %, most preferably from 15 to 30 mole %, based on the total molar amount of the terminal groups of the polycarbonate resin.
• the ratio of the terminal hydroxyl groups can be determined by a method in which the ratio of the terminal hydroxyl groups is directly measured by NMR or a method in which the ratio of the terminal hydroxyl groups is calculated from the molar amount of the terminal hydroxyl groups and the total molar amount of the terminal groups, which are measured by titanium method, UV method, or IR method.
• the resin composition of the present invention can be produced by adding, to 100 parts by weight of (A) an aromatic polycarbonate resin, 0.01 to 0.1 part by weight of (B) a partial ester obtained from a saturated aliphatic carboxylic acid having 10 to 30 carbon atoms and a di- to hexahydric alcohol, wherein the partial ester (B) has an acid value of from 2 to 20 mgKOH.
• the amount of the partial ester (B) is preferably in the range of from 0.015 to 0.08 part by weight, more preferably from 0.02 to 0.06 part by weight.
• the partial ester (B) used in the polycarbonate resin composition of the present invention has an acid value of from 4 to 18 mgKOH, more advantageously from 5 to 15 mgKOH.
• the acid value of the partial ester (B) is not in the range of from 2 to 20 mgKOH, problems arise in that the substrate for an optical information medium produced from the resin composition is likely to exhibit poor mechanical strength and marked occurrence of a cloud.
• the saturated aliphatic carboxylic acid used to form the partial ester (B) it is preferred that the saturated aliphatic carboxylic acid has 10 to 25 carbon atoms, more advantageously 12 to 22 carbon atoms.
• a di- to hexahydric alcohol is used as a polyhydric alcohol for forming the partial ester (B).
• di- to hexahydric alcohols include ethylene glycol, glycerol, trimethylolpropane and pentaerythritol. Of these, especially preferred is glycerol.
• Preferred examples of saturated aliphatic carboxylic acids having 10 to 30 carbon atoms include palmitic acid, stearic acid, eicosanoic acid and behenic acid. Of these, especially preferred are palmitic acid and stearic acid. These saturated aliphatic carboxylic acids can be used individually or in combination.
• the partial ester (B) obtained from the saturated aliphatic carboxylic acid and the di- to hexahydric alcohol
• the partial ester has an acid value of from 2 to 20 mgKOH.
• the partial ester (B) is a monoester. More specifically, it is preferred that the partial ester (B) is at least one member selected from the group consisting of glycerol monostearate, glycerol monopalmitate and pentaerythritol monostearate. It is more preferred that the partial ester (B) is at least one member selected from the group consisting of glycerol monostearate and glycerol monopalmitate.
• the acid value (mgKOH) of a partial ester can be measured by the following method. 100 ml of isopropanol is added to 2.5 g of a partial ester to thereby dissolve the partial ester. To the resultant solution is added phenolphthalein as an indicator. The resultant mixture is subjected to titration using a 0.1 mol/L standard solution of potassium hydroxide, to thereby obtain the acid value (mgKOH) of the partial ester.
• the amount of the partial ester subjected to measurement is changed to 20 g; when it is expected that the partial ester has an acid value of from 1 to 4, the amount of the partial ester subjected to measurement is changed to 10 g; and when it is expected that the partial ester has an acid value of 15 or more, the amount of the partial ester subjected to measurement is changed to 0.5 g.
• the partial ester (B) has an acid value of from 2 to 20 mgKOH.
• the acid value thereof is approximately 1 mgKOH.
• partial ester having an acid value of from 2 to 20 mgKOH
• Such partial ester can be produced, for example, by a method comprising the following two steps:
• a partial ester having an acid value of less than 2 mgKOH is provided.
• commercially available partial esters such as a commercially available monoglyceride of a fatty acid, have an acid value of approximately 1 mgKOH. Therefore, such commercially available partial esters can be provided in step (1).
• a partial ester having an acid value of less than 2 mgKOH can be produced by a conventional method.
• the method for producing a partial ester having an acid value of less than 2 mgKOH is explained, taking as examples the cases where partial esters produced are 1-monoglyceride of a fatty acid and 2-monoglyceride of a fatty acid. (With respect to the details of a method for producing a partial ester having an acid value of less than 2 mgKOH, reference can be made, for example, to Unexamined Japanese Patent Application Laid-Open Specification No. Sho 51-65705.)
• 1-Monoglyceride of a fatty acid can be produced by a method in which 1,2-isopropylidene glycerol and a fatty acid chloride are subjected to a reaction, and the resultant reaction product (i.e., an ester) is treated with an inorganic acid.
• 2-monoglyceride of a fatty acid can be produced by a method in which 1,3-benzylidene glycerol and a fatty acid chloride are subjected to a reaction, and the resultant reaction product (i.e., an ester) is subjected to a catalytic reduction.
• Each of the thus obtained 1-monoglyceride of a fatty acid and 2-monoglyceride of a fatty acid has an acid value of less than 2 mgKOH, wherein, in general, the acid value is approximately 1 mgKOH.
• step (2) above the acid value of the partial ester (having an acid value of less than 2 mgKOH) which is provided in step (1) above, is increased to a value in the desired range (of from 2 to 20 mgKOH), to thereby obtain the desired partial ester (i.e., the partial ester (B)).
• the acid value can be increased by the following method.
• the partial ester having an acid value of less than 2 mgKOH provided in step (1) above is placed in a container purged with nitrogen gas.
• the container containing the partial ester is heated at a temperature of from 150 to 200° C.
• the partial ester in the container is stirred in the molten state while keeping the internal temperature of the container in the above-mentioned range, thereby increasing the acid value of the partial ester.
• the stirring under heating is continued, and samples are taken from the partial ester in the molten state at regular intervals (e.g., every 1 hour) for the measurement of the acid value by the above-mentioned measuring method. By performing the measurement of the acid values of the samples, the increase in the acid value can be confirmed.
• the desired partial ester can be obtained.
• the time needed for the acid value of the partial ester (which is stirred in the molten state) to reach a value in the desired range i.e., the time for which the stirring of the partial ester in the molten state is performed
• the time for the stirring is at least five hours.
• the resin composition of the present invention can be produced by subjecting the aromatic polycarbonate resin (A) and the partial ester (B) to melt-kneading by the conventional method using, for example, a conventional extruder or mixing machine, such as a single-screw extruder, a multi-screw extruder, a Banbury mixer, or a kneader.
• a conventional extruder or mixing machine such as a single-screw extruder, a multi-screw extruder, a Banbury mixer, or a kneader.
• the melt-kneading temperature is generally in the range of from 230 to 330° C.
• the resin composition of the present invention may contain an additive, such as a heat stabilizer, an antioxidant, a weathering stabilizer, a UV absorber, a mold release agent, a lubricant, an antistatic agent, a plasticizer and an acidic compound having a pKa value of 5 or less.
• an additive such as a heat stabilizer, an antioxidant, a weathering stabilizer, a UV absorber, a mold release agent, a lubricant, an antistatic agent, a plasticizer and an acidic compound having a pKa value of 5 or less.
• an additive may be charged into a reactor containing the polycarbonate resin in the molten state after completion of the polymerization reaction for producing the polycarbonate resin.
• the mixing of an additive with the other components of the resin composition may be performed by a method in which the produced polycarbonate is first pelletized and, then, an additive is mixed with the resultant pellets, whereupon the resultant mixture of the pellets and the additive is subjected to melt-kneading.
• additives may be used in an amount generally employed in the conventional polycarbonate resin composition.
• heat stabilizers include phosphorus compounds, phenolic compounds, sulfur compounds, epoxy compounds, hindered amines and acidic compounds.
• Examples of phosphorus compounds which can be used as the heat stabilizer include phosphorus-containing acids, phosphorous esters, phosphinic esters, phosphoric esters and phosphonic esters.
• Examples of phosphorus-containing acids include phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, a polyphosphoric acid and phosphinic acids.
• Examples of phosphorous esters include phosphorous triesters, phosphorous diesters and phosphorous monoesters.
• Preferred examples of phosphorous triesters include tris(2,4-di-t-butylphenyl)phosphite, tris(nonylphenyl)phosphite, tris(dinonylphenyl)phosphite, triphenyl phosphate, tetraphenyldipropylene glycol phosphite, tetra(tridecyl)-4,4′-isopropylidenediphenyl diphosphite, bis(tridecyl)pentaerythritol diphosphite, bis(nonylphenyl)pentaerythritol diphosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, distearyl pentaeryth
• Preferred examples of phosphorous diesters include diphenylhydrogen phosphite, bis(nonylphenyl)hydrogen phosphite, bis(2,4-di-t-butylphenyl)hydrogen phosphite, dicresylhydrogen phosphite, bis(p-t-butylphenyl)hydrogen phosphite, and bis(p-hexylphenyl)hydrogen phosphite.
• Preferred examples of phosphorous monoesters include phenyldihydrogen phosphite, nonylphenyldihydrogen phosphite and 2,4-di-t-butylphenyldihydrogen phosphite.
• phenolic compounds which can be used as the heat stabilizer include 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-p-anisole, 2,6-di-t-butyl-4-ethylphenol, 2,2′-methylenebis(6-t-butyl-p-cresol), 2,2′-methylenebis(4-ethyl-6-t-butyl-p-phenol), 4,4′-methylenebis(6-t-butyl-p-cresol), 4,4′-butylidenebis(6-t-butyl-m-cresol), tetrakis(methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate)methane, 4,4′-thiobis(6-t-butyl-m-cresol), stearyl- ⁇ -(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 1,
• sulfur compounds which can be used as the heat stabilizer include benzensulfinic acid, p-toluenesulfinic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, and methyl, ethyl, butyl, octyl or phenyl esters thereof.
• sulfur compounds which can be used as the heat stabilizer include dilauryl-3,3′-thiodipropionate, ditridecyl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate and pentaerythritol( ⁇ -lauryl thiopropionate).
• epoxy compounds which can be used as the heat stabilizer include fats and oils, such as epoxidized soybean oil and epoxidized linseed oil; glycidyl compounds, such as phenyl glycidyl ether, allyl glycidyl ether, t-butylphenyl glycidyl ether, diglycidyl ether of bisphenol A, diglycidyl ether of tetrabromobisphenol A, diglycidyl phthalate and diglycidyl hexahydrophthalate; epoxycyclohexane compounds, such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 2,3-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 4-(3,
• inorganic acids such as boric acid
• organic acids such as adipic acid, citric acid and acetic acid
• sulfonic acids such as benzenesulfonic acid and p-toluenesulfonic acid
• sulfonic esters such as ethyl benzenesulfonate and butyl p-toluenesulfonate.
• the heat stabilizers may be used individually or in combination. With respect to the amount of the heat stabilizer, there is no particular limitation.
• the amount of the heat stabilizer is generally from 0.0005 to 0.05 part by weight, preferably from 0.001 to 0.04 part by weight, more preferably from 0.005 to 0.03 part by weight, relative to 100 parts by weight of the polycarbonate resin (A).
• the polycarbonate resin composition of the present invention for use in the production of a substrate for an optical information medium can be advantageously used for the production of a disc-shaped substrate (having a thickness of 1.2 mm or less) for an optical information medium, such as a CD, a CD-R, a CD-RW, an MD, an MO, a DVD or a DVD-RAM.
• a disc-shaped substrate having a thickness of 1.2 mm or less
• an optical information medium such as a CD, a CD-R, a CD-RW, an MD, an MO, a DVD or a DVD-RAM.
• the substrate can be produced by subjecting the polycarbonate resin composition of the present invention to an injection molding using an injection molding machine for producing optical discs.
• the injection molding is performed under conditions wherein the molding temperature is from 300 to 390° C., the mold temperature is from 40 to 130° C., and the molding cycle time is from 2 to 15 seconds.
• the injection molding machine for producing optical discs a conventional one can be used.
• the weight average molecular weight of a polycarbonate resin was measured by gel permeation chromatography (GPC) using tetrahydrofuran (as a solvent) and a polystyrene gel column.
• GPC gel permeation chromatography
• the reversed phase liquid chromatography was performed, using a 991L UV detector (manufactured and sold by Waters Corporation, U.S.A) and Inertsil ODS-3 column (registered trade mark, manufactured and sold by GL Science Inc., Japan).
• a mixture of methanol and 0.1 weight % aqueous solution of phosphoric acid was used as an eluent, and measurement was carried out by gradient elution technique at a gradient wherein the volume ratio (methanol/0.1 weight % aqueous solution of phosphoric acid) is changed from 20/80 at the start to 100/0.
• the absorbance at 300 nm was measured using the UV detector.
• Absorbance coefficients for determining recurring unit (1) and heterounit (2′) were obtained by using a standard compound (as a standard compound, a hydroxy compound having a structure formed by hydrolysis of heterounit (2′) was used).
• the amount of the partial ester subjected to measurement was changed to 20 g; when it was expected that the partial ester had an acid value of from 1 to 4, the amount of the partial ester subjected to measurement was changed to 10 g; and when it was expected that the partial ester had an acid value of 15 or more, the amount of the partial ester subjected to measurement was changed to 0.5 g.
• a disc-shaped substrate (thickness: 1.2 mm) for a CD-R (hereinafter, this substrate is frequently referred to simply as a “CD-R substrate disc”), which had microgrooves formed on the surface thereof, was produced by subjecting a polycarbonate resin composition to an injection molding, using an injection molding machine for producing optical discs (MDM1; manufactured and sold by Meiki Co., Ltd., Japan), under conditions wherein the molding temperature was 330° C., the mold temperature was 100° C., and the molding cycle was 5 seconds (i.e., high-cycle molding).
• MDM1 manufactured and sold by Meiki Co., Ltd., Japan
• the birefringence (nm) of a CD-R substrate disc is defined by the difference between the maximum value and minimum value of refractive index values as measured in the radial direction of the disc. It is desirable that the birefringence value of a CD-R substrate disc is not more than 40 nm.
• Transferability (%) ( D 1 /D 2 ) ⁇ 100
• the anti-cloud properties were measured by a method in which 100 CD-R substrate discs were subjected to sputtering with aluminum on the microgrooved faces of the discs, and the resultant sputtered, microgrooved faces of the discs were observed to examine whether or not a cloud occurred.
• the anti-cloud properties of the resin composition were evaluated, based on the number of discs in which the occurrence of a cloud was observed, in accordance with the following criteria:
• the anti-cloud properties of a CDR substrate disc are evaluated to be either “ ⁇ : Occurrence of a cloud was not observed” or “ ⁇ : Occurrence of a cloud was observed in 1 to 3 discs”.
• Glycerol monostearates having acid values of 1 mgKOH, 8 mgKOH, 12 mgKOH, 17 mgKOH and 25 mgKOH, respectively:
• glycerol monostearate (Rikemal S-100; manufactured and sold by Riken Vitamin Co., Ltd., Japan) having an acid value of 1 mgKOH.
• This commercially available product as such was used as a glycerol monostearate having an acid value of 1 mgKOH.
• the acid value of this commercially available glycerol monostearate was increased by the following method. The glycerol monostearate was placed in a container purged with nitrogen gas. The container containing the glycerol monostearate was heated at a temperature of from 150 to 200° C.
• the glycerol monostearate in the container was stirred in the molten state while keeping the internal temperature of the container in the above-mentioned range, thereby increasing the acid value of the glycerol monostearate.
• the stirring under heating was continued, and sampling of the glycerol monostearate in the molten state was performed at intervals of 1 hour for the measurement of the acid value by the above-mentioned measuring method. By performing the measurement of the acid values of the samples, the increase in the acid value was confirmed.
• pentaerythritol monostearate (Rikester EW-440A; manufactured and sold by Riken Vitamin Co., Ltd., Japan) having an acid value of 1 mgKOH.
• the acid value of this commercially available pentaerythritol monostearate was increased in substantially the same manner as in the case of the above-mentioned commercially available glycerol monostearate, to thereby obtain pentaerythritol monostearate having an acid value of 5 mgKOH.
• glycerol monopalmitate (Rikemal P-100; manufactured and sold by Riken Vitamin Co., Ltd., Japan) having an acid value of 1 mgKOH.
• the acid value of this commercially available glycerol monopalmitate was increased in substantially the same manner as in the case of the above-mentioned commercially available glycerol monostearate, to thereby obtain glycerol monopalmitate having an acid value of 13 mgKOH.
• glycerol tristearate (Rikemal VT; manufactured and sold by Riken Vitamin Co., Ltd., Japan) having an acid value of 1 mgKOH.
• the acid value of this commercially available glycerol tristearate was increased in substantially the same manner as in the case of the above-mentioned commercially available glycerol monostearate, to thereby obtain glycerol tristearate having an acid value of 3 mgKOH.
• the polymerization was performed in the continuous manner, except that only the two dissolving/mixing tanks for raw materials were operated alternately in the batch-wise manner.
• Each of the two dissolving/mixing tanks for raw materials was operated under conditions wherein the heating temperature was 180° C., the pressure was atmospheric pressure, and nitrogen gas (oxygen concentration: 0.5 ppm) was flowed at a flow rate of 1 liter/hr to prevent the intrusion of air into the tank.
• 80 kg of a powdery mixture of particulate bisphenol A and particulate diphenyl carbonate (diphenyl carbonate/bisphenol A molar ratio: 1.10) was provided and placed in a vacuum of 40 mmHg, and the air contained in the mixture was purged with nitrogen gas five times.
• the thus treated powdery mixture of the raw materials and 7 mg of sodium hydroxide were charged into the dissolving/mixing tank for raw materials, and the contents of the tank were melted and stirred for 5 hours for homogeneous mixing before being transferred to the next step.
• the first vertical agitation type polymerizer vessel was operated under conditions wherein the reaction temperature was 234° C., the reaction pressure was 98 mmHg, and the liquid volume in the polymerizer vessel was maintained at 20 liters.
• the second vertical agitation type polymerizer vessel was operated under conditions wherein the reaction temperature was 250° C., the reaction pressure was 6 mmHg, and the liquid volume in the polymerizer vessel was maintained at 20 liters.
• the twin-screw horizontal agitation type polymerizer vessel was operated under conditions wherein the reaction temperature was 260° C., the reaction pressure was 2.0 mmHg, and the liquid volume in the polymerizer vessel was maintained at 10 liters.
• the wire-wetting fall polymerizer was operated under conditions wherein the reaction temperature was 260° C., the reaction pressure was 1.0 mmHg, and the volume of the reaction mixture obtained at the bottom of the polymerizer was maintained at 20 liters.
• an aromatic polycarbonate resin was produced.
• the measurement of the weight average molecular weight and of the amount of the heterounit (2′) were performed. As a result, it was found that the weight average molecular weight was 15,600 and the amount of the heterounit (2′) was 0.13 mole %, based on the total molar amount of the recurring units (1).
• substrate discs were produced, and the obtained substrate discs were used for the evaluation of the properties of the resin composition.
• the results of the evaluation are shown in Table 1 below.
• the substrate discs exhibited excellent properties; specifically, the transferability was 100%, the birefringence was from 0 to 10 nm, there was no occurrence of a cloud, and high mechanical strength was exhibited.
• Example 1 100 Parts by weight of the polycarbonate resin obtained in Example 1, 0.02 part by weight of tris(2,4-di-t-butylphenyl)phosphite and 0.03 part by weight of glycerol monostearate having an acid value of 12 mgKOH were subjected to melt-kneading using a twin-screw extruder (model name: PCM30; manufactured and sold by Ikegai Ltd., Japan) (barrel temperature: 280° C.), to thereby obtain a polycarbonate resin composition.
• a twin-screw extruder model name: PCM30; manufactured and sold by Ikegai Ltd., Japan
• substrate discs were produced, and the obtained substrate discs were used for the evaluation of the properties of the resin composition.
• the results of the evaluation are shown in Table 1 below.
• the substrate discs exhibited excellent properties; specifically, the transferability was 100%, the birefringence was from 0 to 10 nm, there was no occurrence of a cloud, and high mechanical strength was exhibited.
• Polycarbonate resin compositions were produced in substantially the same manner as in Example 1, except that the fatty acid ester (partial ester) was changed as shown in Table 1.
• the substrate discs produced in Comparative Example 1 exhibited a transferability of 100% and a birefringence of from 10 to 30 nm.
• the substrate discs produced in Comparative Example 2 exhibited a transferability of 100% and a birefringence of from 10 to 25 nm.
• the substrate discs produced in Comparative Example 3 exhibited a transferability of 90% and a birefringence of from 10 to 30 nm.
• the substrate discs produced in Comparative Example 4 exhibited a transferability of 100% and a birefringence of from 10 to 30 nm.
• the substrate discs produced in Comparative Example 5 exhibited a transferability of 100% and a birefringence of from 10 to 40 nm.
• Polycarbonate resin compositions were produced in substantially the same manner as in Example 1, except that the reaction pressure in the wire-wetting fall polymerizer was changed to 1.4 mmHg (for Comparative Example 6) and 0.8 mmHg (for Comparative Example 7).
• a polycarbonate resin composition was produced in substantially the same manner as in Example 1, except that the twin-screw horizontal agitation type polymerizer vessel was operated under conditions wherein the reaction temperature was 270° C. and the reaction pressure was 4.0 mmHg; that the wire-wetting fall polymerizer was operated under conditions wherein the reaction temperature was 270° C. and the reaction pressure was 2.0 mmHg; and that the amount of glycerol monostearate used as a partial ester was changed to 0.03 part by weight.
• substrate discs were produced, and the obtained substrate discs were used for the evaluation of the properties of the resin composition.
• the results of the evaluation are shown in Table 1 below.
• the substrate discs exhibited excellent properties; specifically, the transferability was 100%, the birefringence was from 0 to 10 nm, and high mechanical strength was exhibited.
• the obtained polycarbonate had a weight average molecular weight of 6,800.
• the thus obtained polycarbonate and acetone were fed to a co-rotating intermeshing twin-screw kneader (having two screws rotating in the same direction), wherein the feeding rates of the polycarbonate and aceton were, respectively, 1.5 kg/hr and 0.8 kg/hr, to thereby obtain a crystallized polycarbonate.
• the obtained crystallized polycarbonate was dried. 15 kg of the resultant dried crystallized polycarbonate was charged into a 70-liter, tumbler type, solid-state polymerizer, and a reaction was performed at 220° C. under a pressure of 2 mmHg for 4 hours, to thereby obtain a polycarbonate.
• the obtained polycarbonate had a weight average molecular weight of 14,800.
• substrate discs were produced, and the obtained substrate discs were used for the evaluation of the properties of the resin composition.
• the results of the evaluation are shown in Table 1 below.
• the substrate discs exhibited excellent properties; specifically, the transferability was 100%, the birefringence was from 0 to 10 nm, there was no occurrence of a cloud, and high mechanical strength was exhibited.
• Example 1 100 Parts by weight of the polycarbonate resin obtained in Example 1 and 0.03 part by weight of glycerol monopalmitate having an acid value of 13 mgKOH were subjected to melt-kneading using a twin-screw extruder (model name: PCM30; manufactured and sold by Ikegai Ltd., Japan) (barrel temperature: 280° C.), to thereby obtain a polycarbonate resin composition.
• a twin-screw extruder model name: PCM30; manufactured and sold by Ikegai Ltd., Japan
• substrate discs were produced, and the obtained substrate discs were used for the evaluation of the properties of the resin composition.
• the results of the evaluation are shown in Table 1 below.
• the substrate discs exhibited excellent properties; specifically, the transferability was 100%, the birefringence was from 0 to 10 nm, there was no occurrence of a cloud, and high mechanical strength was exhibited.
• Example 1 100 Parts by weight of the polycarbonate resin obtained in Example 1, 0.015 part by weight of glycerol monostearate having an acid value of 8 mgKOH and 0.02 part by weight of pentaerythritol monostearate having an acid value of 5 mgKOH were subjected to melt-kneading using a twin-screw extruder (model name: PCM30; manufactured and sold by Ikegai Ltd., Japan) (barrel temperature: 280° C.), to thereby obtain a polycarbonate resin composition.
• a twin-screw extruder model name: PCM30; manufactured and sold by Ikegai Ltd., Japan
• substrate discs were produced, and the obtained substrate discs were used for the evaluation of the properties of the resin composition.
• the results of the evaluation are shown in Table 1 below.
• the substrate discs exhibited excellent properties; specifically, the transferability was 100%, the birefringence was from 0 to 10 nm, there was no occurrence of a cloud, and high mechanical strength was exhibited.
• a polycarbonate resin composition was produced in substantially the same manner as in Example 6, except that 0.02 part by weight of tris(2,4-di-t-butylphenyl)phosphite was additionally used as a component.
• substrate discs were produced, and the obtained substrate discs were used for the evaluation of the properties of the resin composition.
• the results of the evaluation are shown in Table 1 below.
• the substrate discs exhibited excellent properties; specifically, the transferability was 100%, the birefringence was from 0 to 10 nm, there was no occurrence of a cloud, and high mechanical strength was exhibited.
• the polycarbonate resin composition of the present invention in the production of a substrate for an optical information medium is advantageous in that a substrate (for an optical information medium) which has high mechanical strength and in which the occurrence of a “cloud” (i.e., haze) is suppressed, can be produced by the so-called “high-cycle molding” (i.e., the molding can be performed with a short cycle time).
• the polycarbonate resin composition of the present invention can be very advantageously used in the production of a substrate for an optical information medium, such as an optical disc (e.g., a CD or a DVD).

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